1. Field of the Invention
The present invention relates to display devices, and particularly, to display devices equipped with light-emitting elements having light-emitting layers and to image-information processing apparatuses equipped with such display devices.
2. Description of the Related Art
Referring to FIG. 13, in a display device (referred to as “organic electroluminescent (EL) display device” hereinafter) equipped with organic EL elements, multiple organic EL elements are generally arranged on a substrate 100 provided with a driving circuit, and the surface of each organic EL element is covered with a protection layer 600. Each organic EL element is constituted of a first electrode 200, a second electrode 500, and an organic compound layer 400 including a light-emitting layer interposed between these electrodes. A light-emitting area of each organic EL element is defined by a partition layer 300. The organic EL elements are covered with the protection layer 600 so as to be protected from degradation caused by moisture and oxygen contained in the external space.
In the display device shown in FIG. 13, light (luminescent light) emitted at various angles from the organic EL elements mainly undergoes total reflection at the boundary between the protection layer 600 and the external space, which is a problem in that half or more of the luminescent light cannot be emitted outward from the organic EL display device. Moreover, in an environment where light (external light) is received from the outside, the external light entering the display device is emitted outward therefrom after being reflected at an interface of a multilayer film or a metal layer constituting the wires in the driving circuit or the first reflective electrodes. Therefore, an observer may observe both the external light reflected within the display device and the luminescent light emitted to the outside, which is a problem in terms of reduced legibility (contrast and view angle characteristics).
For solving these problems, Japanese Patent Laid-Open No. 2004-205849 discloses an organic EL display device in which a lens array constituted of multiple lenses is arranged on the surface of the device, a reflection prevention film is provided over the surface of each lens, and a polarizer is disposed in parallel to the substrate at the light emission side of the lenses. With this configuration, the total reflection occurring at the boundary between the display device and the external space can be reduced by the lens array so as to achieve increased light emission efficiency. In addition, the reflection of external light can also be reduced by the reflection prevention film and the polarizer.
Japanese Patent Laid-Open No. 2004-127661 discloses an organic EL display device equipped with lenses in correspondence with organic EL elements. In this organic EL display device, a black mask having multiple openings in correspondence with the organic EL elements is disposed between a passivation layer and a lens sheet. With this configuration, light emitted from a certain organic EL element is prevented from entering the lens provided in correspondence with an adjacent organic EL element, thereby reducing legibility in directions other than the normal direction of the substrate.
A circular polarization member (polarizer) can quench a component of light passing through the circular polarization member in the normal direction, whether the light be external light entering the display device from the outside or external light reflected within the display device so as to be emitted to the outside again. However, a light component that obliquely passes through the circular polarization member (at an angle relative to the normal direction) or a light component having passed through the circular polarization member at an angle cannot be quenched.
Because a display device is often observed from the front, that is, in the normal direction of the substrate, high legibility in the normal direction is required. In the case of the display device according to Japanese Patent Laid-Open No. 2004-205849, external light incident on the substrate at an angle, that is, external light having passed through the circular polarization member at an angle, due to refraction by the lenses is reflected within the display device so as to be emitted outward in the normal direction of the substrate. When such external light enters the display device, since the external light includes a component of light having passed through the circular polarization member at an angle, the light is emitted outward from the display device in the normal direction without being sufficiently quenched by the circular polarization member, leading to reduced legibility. In other words, in the display device having lenses as discussed in Japanese Patent Laid-Open No. 2004-205849, the external light reflected within the display device cannot be sufficiently suppressed by the polarizer (circular polarization member) alone.
The black mask in Japanese Patent Laid-Open No. 2004-127661 is not positioned in view of suppressing the external light emitted outward in the normal direction of the substrate via the lenses after entering the display device via the lenses and being reflected within the display device.